Meltblown fibers can be manufactured with very fine diameters, in the range of 1-10 microns, which is very advantageous in forming various kinds of non-woven fabrics. However, meltblown fibers are relatively weak in strength. To the contrary, spunbond fibers can be manufactured to be very strong but have a much larger diameter, in the range of 15-50 microns. Fabrics formed from spunbond are less opaque and tend to exhibit a rough surface since the fiber diameters are quite large. In addition, spinning of thermoplastic resins through a multi-row spinnerette, according to the teachings in U.S. Pat. No. 5,476,616 issued to Schwarz, is quite challenging because of the fast solidification of the outer rows and/or columns of filaments. Due to this fast solidification in the outer rows and/or columns, the filaments tend to be larger and/or form rope defects with adjacent inner rows and/or columns of filaments. U.S. Ser. Nos. 14/271,638; 14/271,655 and 14/271,675 all filed on the same day by Brown et al. and assigned to Biax-Fiberfilm Corporation, teaches forming a non-woven web and an apparatus and method for forming the web from spun-blown® fibers with minimal roping.
Up until now, no one has been able to successfully spin thermoplastic resins of high molecular weight and high viscosity through fine capillaries and attenuate them with high speed air retained at a temperature ranging from between about 0° C. to about 250° C., colder or hotter, than polymer melt temperatures. By being able to do this, one can obtain spun-blown® fibers which have a diameter similar to the diameters of meltblown fibers but which exhibit strength properties approaching those of spunbond fibers. Because the spun-blown® fibers are fine and strong, a smaller quantity of them can be comingled with a first material, such as staple/pulp fibers, to form an inexpensive, hybrid non-woven web.
Now, a hybrid non-woven web has been invented along with an apparatus and method for forming such a web. The hybrid non-woven web includes a matrix of a first material and first and second spun-blown® fibers. Each of the first and second spun-blown® fibers are formed from a thermoplastic composition that contains at least one polymer having a melt flow rate of from between about 5 grams/10 minutes to about 6,000 grams/10 minutes at 230° C., an average diameter of between about 1 microns to 10 microns, and a standard deviation of from between about 0.9 microns to about 5 microns. The hybrid non-woven web also has a tensile strength of at least about 5 gf/gsm/cm width, measured in a machine direction. Because the first and second spun-blown® fibers are of high strength, a smaller quantity of them are needed to fabricate the hybrid non-woven web. In addition, a new class of hybrid non-woven structures can be produced which will exhibit excellent tensile and absorption properties.